Mechanisms involved in mineral oil plasmacytomagenesis in the BALB/c mouse is the principle problem of the laboratory. Plasmacytomagenesis appears to be a 2-staged process. Stage 1 involves the formation of transformed cells, stage 2 involves the selective proliferation of these cells. Specific genes determine susceptibility to transformation. The oil granuloma provides an essential micro-environment for early growth of plasmacytoma cells. From crosses of the plasmacytomagenesis resistant DBA/2 and susceptible BALB/c multiple congenic strains are being developed to identify resistance genes. Studies continue to determine the role of type C viruses in initiating plasma cell transformation. The specific gene product of Abelson virus is being sought. Micro-environmental growth dependency is being studied, in millipore diffusion chambers where the role of specific cells and factors can be determined. Immunochemical studies of myeloma proteins continue to determine: 1) the number of V-kappa isotype groups in the mouse; and 2) to build spacefilling hypothetical models of antigen binding myeloma proteins.